The purpose of this study is to investigate whether mindfulness was mediated in the relationship between job stress and job satisfaction of professional counselors. For this purpose, a statistical analysis was performed by conducting random sampling surveys on 248 professional counselors who work in elementary, middle, or high schools. The main results are the followings: First, the professional counselors’ job stress was found to have a negative correlation with their job satisfaction and mindfulness. Second, the mindfulness was found to partially mediate the relationship between the job stress and the job satisfaction, and it was verified as a significant parameter. Therefore, in order to increase the job satisfaction of professional counselors, it is necessary to explore methods to reduce the job stress, to understand the duties and roles of professional counselors in the school field, and to recognize the necessity of school counseling. Furthermore, in order to improve the quality of life and education of professional counselors, it is necessary to explore methods to strengthen individual internal competencies such as the mindfulness and to provide support and education for various training programs for this purpose.